The present invention relates generally to improvements in automatic locking safety belt retractors used in vehicles and it relates more particularly to an improved acceleration responsive automatic locking belt retractor provided with a mechanism for sensing the change of movement of a vehicle and locking the seat belt against extraction in response to a predetermined acceleration.
There are various types of conventional vehicle safety or restraint retractors which lock a seat belt in response to a sharp change in the speed of the vehicle when it collides with an object. In conventional retractors, however, the acceleration sensitivity is very high and the acceleration sensing mechanism is repeatedly actuated and deactuated at a high frequency. Consequently, for example, in a mechanism in which a ratchet wheel rotating with the belt retraction reel is engaged with a pawl to lock the reel and seat belt, it occasionally happens that the tips of the teeth of the ratchet wheel and the pawl tooth or tip are momentarily in the same position. In such an event, the tips of the ratchet wheel teeth, the rotational speed of which has been greatly increased by the belt withdrawing force outwardly kick or impel the pawl tooth so as to prevent the pawl from engaging the ratchet wheel. As a result, the belt is withdrawn a considerable and excessive amount by the time the pawl has returned to a proper position where it can engage the ratched wheel. The above occurrence substantially prevents the proper and reliable functioning of the seat belt. In some cases, the teeth of the ratchet wheel or the pawl tooth are damaged to thereby prevent a complete and proper engagement therebetween.
The applicant has previously proposed an automatic locking retractor reel in which the above-mentioned drawbacks encountered in conventional reels are eliminated and in which a pawl is not employed. In such a retractor, a stop member is provided which has a claw portion of projection engageable with and disengageable from the teeth of the ratchet wheel which rotates with the reel. When this stop member is moved in response to the displacement or acceleration of the vehicle to transfer the claw portion thereof from a non-engage position to an engage position, the withdrawal of seat belt is locked or stopped. However, the aforesaid retractor structure lacks a stop member receiving guide surface, the upward movement of the stop member being regulated by a long slot and a stop pin. In this retractor structure, the deterioration and wear of the stop member due to the repeated engaging impact actions cannot be avoided and a safe and reliable operation is not achieved.